Embryonic stem (ES) and induced pluripotent stem (iPS) cells hold enormous potential for diverse medical applications, limited primarily by our methods to direct the activities of these cells toward specific therapeutic goals. A more complete understanding of the regulatory circuitry of pluripotent stem cells would almost certainly provide insights useful to overcome this limitation. We propose to expand knowledge of the transcriptional regulatory circuitry of murine and human embryonic stem (ES) cells by identifying novel ES cell transcription factors, chromatin regulators and signaling proteins and by determining how they function together to control the gene expression program responsible for pluripotency and self-renewal. Furthermore, we propose to use improved understanding of the control of ES cell state to develop more powerful methods for cellular reprogramming to generate iPS cells. To accomplish these goals, the specific aims of the proposal are: 1) Combine and further develop powerful experimental and analytical technologies that can identify novel regulators of ES cell state and determine their genome-wide occupancy and function; 2) Identify novel transcription factors, chromatin regulators and signaling proteins that play key roles in murine and human ES cell identity; 3) Determine how novel transcription factors, chromatin regulators and signaling proteins contribute to pluripotency and self-renewal in murine and human ES cells; and 4) Use cellular reprogramming assays to gain insights into the control of cell state and to develop more powerful methods for cellular reprogramming. Improved understanding of transcriptional regulatory circuitry from these studies will lead to new insights into the control of ES cell state, reveal how key regulators control the gene expression program of ES cells, facilitate efforts to manipulate cell fates for regenerative medicine, and provide the foundation for further mapping regulatory circuitry in human and other vertebrate cells.